Terahertz Wave Generation from DC Field-applied Hollow Air-plasmas

Air-plasma is a powerful and convenient laboratory terahertz (THz) source that can be achieved by focusing a laser beam to ionize gaseous molecules in air. Nowadays, different attempts have been made to modulate the THz output of air-plasma, for instance, by using the dual-color laser pulses instead of the one-color scheme [1], by applying a DC-field on the air-plasma [2], or by shaping the spatial distribution of the air-plasma [3], Both the dual-color and DC-field-applied strategies contribute to greatly increase the THz output from air-plasma, due to the net electron currents accumulating under the laser actions.